sounding board is a noun meaning "a person whose reactions to something serve as an indication of its acceptability". It carries 2 recorded senses.
a person whose reactions to something serve as an indication of its acceptability
“I would use newspapermen as a sounding board for such policies”
(music) resonator consisting of a thin board whose vibrations reinforce the sound of the instrument
music
Definitions, synonyms and semantic relations for sounding board come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.